-14 is continually formed in nature by the interaction of neutrons with nitrogen-14 in the Earth’s atmosphere; the neutrons required for this reaction are produced by cosmic rays interacting with the atmosphere.
Radiocarbon present in molecules of atmospheric : it is absorbed from the air by green plants and then passed on to animals through the food chain.
Carbon-14 is an unstable isotope of carbon that will eventually decay at a known rate to become carbon-12.
Cosmic rays – high energy particles from beyond the solar system – bombard Earth’s upper atmosphere continually, in the process creating the unstable carbon-14. Because it’s unstable, carbon-14 will eventually decay back to carbon-12 isotopes.
It can be used on objects as old as about 62,000 years.